The invention concerns a method for reconnection and connection of sensor groups, and more particularly hydrophone groups or channels in a seismic streamer where the active sections in the seismic streamer are connected with electronic modules or with one another via connector plugs.
In marine seismic surveys data acquisition is normally conducted by towing behind a vessel a so-called hydrophone cable or seismic streamer which is composed of a number of active sections containing hydrophone groups, the active sections usually being separated by passive sections. A typical seismic streamer may have a length of 3-4 km and the number of active sections may be, e.g., 48 or 96 or more. Each active section comprises a number of hydrophone groups, these groups varying in length from, e.g., a few meters up to 100 meters and comprising 20-100 hydrophones or more. The typical number of hydrophone groups or channels in a seismic streamer can therefore be approximately 1000.
The extent of the hydrophone groups and the distance between their centers affect the spatial resolution which can be achieved in a marine seismic survey. In order to obtain an optimum data recording, every effort is made to reduce to a minimum the number of channels used and thereby the amount of data which has to be stored for further processing, without any of the vital and required information on the subterranean structures being lost.
In accordance with prior art the active sections are built up to a typical length of 100 meters with specific group lengths of, e.g., 6.25 meters or 12.5 meters. The sections are connected via electronic modules, thus forming a seismic streamer several kilometers in length. The object of the electronic modules is to provide a digitalization and further transfer of the analog signals recorded by the hydrophone groups to the data recording system aboard the vessel which is towing the seismic streamer. In order to increase the group length, the hydrophone groups are connected together two by two in parallel by means of so-called program plugs or processor modules. It is also possible to connect more than two hydrophone groups together. The connected groups are summed, e.g., two by two in the program plugs or processor modules and the groups thus summed are then fed into the electronic module for further transfer to the data equipment on the towing vessel.
The disadvantage of connecting hydrophone groups in this manner is the use of extra connector plugs and program plugs which are exposed to sea water, thus resulting in an increased risk of water penetration leading to faults such as short circuiting of the connector plugs. This reduces the reliability of the marine seismic survey and will probably lead to interruptions of the survey which can be extremely expensive.